STRUCTURAL REINFORCEMENT ELEMENT FOR WOODEN CHAIRS
Field of application
The present industrial utility model relates to a structural reinforcement element made of steel for the frame of a wooden chair and/or armchair. The reinforcement element consists of a steel sheet or plate folded into a C-shape, in which the central part is as long as the internal distance of the seat frame between the front and rear legs and the two wings have folded ends that connect to the two front and rear inner cross-members. The steel reinforcement is applied after assembling the chair and/or armchair having a wooden frame by fixing with suitable fastening means to the inner part of the seat frame.
Background art
In the background art, in the manufacture of chairs with a wooden frame, it has been found that said chairs, if subjected to repeated stresses, fail proximate to the location of the interlocking coupling between the frame of the rear legs and the surface of the seat. This causes limited durability and likewise limited reliability of said chairs.
In order to try to solve this drawback, it has been thought to increase the dimensions of the resisting cross-sections of the material and to apply new kinds of coupling among the various elements that constitute the frame. This, when possible, entails a substantial increase in final price, indeed because thicker solid wood parts are used.
Moreover, wood is a living material, which is susceptible of dimensional variations and expansions in relation to ambient humidity; these drawbacks compromise preservation of the mechanical characteristics of the frame for a long period.
Summary of the model
The aim of the present industrial utility model is to solve the drawbacks noted in frames for chairs or armchairs by increasing their mechanical strength, and therefore also their durability, for an equal resisting cross-section in the most highly stressed points.
The object is to provide a simple reinforcement that is constituted by a metal sheet or plate folded into a C-shape, which is easy to assemble and is locked to the basic frame, in the inner part, by means of conventional fixing systems (for example self-tapping screws, screws and cylindrical fastening blocks). This element is fixed to the inner lateral cross-member of the seat
surface, so that one wing is folded onto the front cross-member of said surface and the other wing is folded onto the rear cross-member, thus reinforcing the regions where the legs are attached. Accordingly, two C-shaped reinforcements are applied in a chair, one on the inner right side and the other on the inner left side.
Essence of the model
The aim and object of the invention are achieved according to the characteristics of the main claim and/or of any other claim cited in this patent text by providing a reinforcement element made of metallic material (for example steel or other material suitable for the purpose) in sheet or plate form, which is folded into a C-shape and can be applied to the concealed inner part of the frame of the seat surface of chairs or armchairs provided with a wooden frame structure.
Said element made of C-shaped folded sheet metal has a central portion that is as long as the internal distance between the front cross-member and the rear cross-member and is as high as, or lower than, the height of the lateral cross-member. The end wings are folded at 90° if the inner frame of the chair is square or rectangular and have a different angle if the frame of the seat surface portion is of the trapezoidal type.
Said reinforcement element is fixed in the inner part of the frame of the seat surface, connecting the front cross-member, the lateral cross-member and the rear cross-member. Accordingly, a chair or armchair requires two reinforcement elements: one which is fixed so as to affect the right inner part and another that affects the left inner lateral part.
The reinforcement element is provided with holes on the end wings for the passage of the screws, while slots for the passage of self-tapping screws are provided in the central portion. In order to provide firm and rigid fixing, particularly on the end wings of the metallic reinforcement, it is necessary to prepare the respective fixing regions on the front and rear cross- members, preferably on the concealed lower side, in order to insert suitable metallic hardware within the body of the cross-members.
The present invention therefore increases the mechanical strength of the wooden frame proximate to the legs, which are vulnerable regions because they are subjected to higher stresses.
In another technical solution, in order to further stiffen the connection between the metal reinforcement element and the frame of the seat surface of the chair, it is possible to use self- tapping corner screws, which are inserted at an angle in the bending point, accordingly connecting directly the plate to the leg.
Furthermore, the reinforcement element can follow the geometric shapes of the inner frame and in particular can follow, in close contact or not, the lateral cross-member of the
structure of the seat surface of the chair.
The present invention is particularly useful in the manufacture of stackable and non- stackable chairs and/or armchairs having a wooden frame structure.
Description of the drawings
This and other characteristics of the present invention become better apparent, by way of preferred non-limiting example, in the two accompanying drawings, wherein:
Figure 1 is a partial perspective view of the frame of the seat surface of a wooden chair, illustrating the two lateral metallic reinforcements;
Figure 2 is a plan view of Figure 1;
Figure 3 is a partial perspective view of the right side of a frame reinforced with the metallic element;
Figure 4 is a plan view of a frame of the seat surface with lateral reinforcement elements, illustrating the application of corner screws proximate to the rear legs;
Figure 5 is a plan view of a reinforcement element with wings folded at an angle other than 90°, suitable to reinforce the frame of the seat surface of a trapezoidal chair;
Figure 6 is a partial perspective view of the right side of a chair frame reinforced with an element and also fixed with corner screws at the rear leg;
Figure 7 is a front view of the C-shaped reinforcement element, illustrating the slots in the central portion;
Figure 8 is a side view of said element, illustrating the screw holes on the end wings;
Figure 9 is a plan view of the same C-shaped reinforcement element shown in Figures 7 and 8, with the end wings folded at 90°.
As shown in the accompanying drawings, the reinforcement element 5 made of metal, preferably steel, is obtained from a sheet or plate and is shaped so as to assume the contour of the inner part of the frame of the seat surface of the stackable or non- stackable chair or armchair.
Said element is approximately C-shaped; the central part is as long as the internal distance between the front and rear cross-members 4, along the lateral cross-member 1, and is provided with slots 9 in order to allow its fixing by means of self-tapping screws 8 to said cross- member. Holes 10 are provided on the end wings 13, which are folded at 90° or at different angles, for the passage of screws 7, which fasten onto appropriately provided cylinders 6 inserted in the body of the front and rear cross-members, or an equivalent technical solution.
In a chair or armchair with a wooden seat surface structure, two reinforcement elements are fixed: one on the inner right side, affecting the front cross-member, the right lateral cross- member, and the rear cross-member 4, and one on the left side, affecting the front cross-member,
the left lateral cross-member, and the rear cross-member.
In chairs in which the frame of the seat surface is rectangular or square, reinforcement elements such as 5 are used, whereas trapezoidal frames use shaped reinforcements 12 with end wings 13 at folding angles other than 90°.
In order to further reinforce the rigid connection between the metallic reinforcement element and the structure of the wood chair, additional locking screws 11 are used proximate to the fold, so as to insert them at an angle in order to anchor the rear leg 2 and/or the front leg 3 to said element.